On 12 July 2016 at 15:53, Jon Hunter <jonathanh@xxxxxxxxxx> wrote:
> The capabilities of the SDHCI host controller are read early during the
> SDHCI host initialisation in sdhci_setup_host() and before any
> regulators for the host have been requested. This means that if the host
> supports some high-speed modes (according to its capabilities register),
> but the board cannot because the appropriate voltage regulator is not
> available, then the host cannot easily override the capabilities that
> are supported.
>
> To allow a SDHCI host controller to determine if it can support high
> speed modes via the presense of the MMC regulators, request the
> regulators before reading the capabilites of the host controller. This
> will allow the SDHCI host to use the 'reset' callback to take the
> appropriate action (set flags, configure registers, etc) before the
> capabilities register(s) are read.
>
> Please note that some SDHCI hosts, such as the Tegra SDHCI host, has
> the ability to mask bits in the capabilities register to prevent
> certain capabilities from being advertised.
>
> Signed-off-by: Jon Hunter <jonathanh@xxxxxxxxxx>
Thanks, applied for next! I changed the minor things pointed out by Adrian.
Kind regards
Uffe
> ---
>
> Although this is described as a "V2" this patch has been added since
> the original patch was posted.
>
> If the below is deemed not appropriate, then another solution I was
> thinking of is to allow the SDHCI host to call 'mmc_regulator_get_supply'
> before calling sdhci_setup_host() and then in sdhci_setup_host() check
> if any regulators are already present before calling
> mmc_regulator_get_supply().
>
> drivers/mmc/host/sdhci.c | 16 +++++++++++-----
> 1 file changed, 11 insertions(+), 5 deletions(-)
>
> diff --git a/drivers/mmc/host/sdhci.c b/drivers/mmc/host/sdhci.c
> index 2ee8bfa77116..628c4b3558c0 100644
> --- a/drivers/mmc/host/sdhci.c
> +++ b/drivers/mmc/host/sdhci.c
> @@ -3021,6 +3021,17 @@ int sdhci_setup_host(struct sdhci_host *host)
>
> mmc = host->mmc;
>
> + /*
> + * If there are external regulators, get them. Note
> + * this must be done early before resetting the host
> + * and reading the capabilities so that the host can
> + * take the appropriate action if regulators are not
> + * available.
> + */
> + ret = mmc_regulator_get_supply(mmc);
> + if (ret == -EPROBE_DEFER)
> + return ret;
> +
> sdhci_read_caps(host);
>
> override_timeout_clk = host->timeout_clk;
> @@ -3253,11 +3264,6 @@ int sdhci_setup_host(struct sdhci_host *host)
> mmc_gpio_get_cd(host->mmc) < 0)
> mmc->caps |= MMC_CAP_NEEDS_POLL;
>
> - /* If there are external regulators, get them */
> - ret = mmc_regulator_get_supply(mmc);
> - if (ret == -EPROBE_DEFER)
> - goto undma;
> -
> /* If vqmmc regulator and no 1.8V signalling, then there's no UHS */
> if (!IS_ERR(mmc->supply.vqmmc)) {
> ret = regulator_enable(mmc->supply.vqmmc);
> --
> 2.1.4
>
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